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中國(guó)地質(zhì)大學(xué)長(zhǎng)城學(xué)院
本科畢業(yè)設(shè)計(jì)外文資料翻譯
系 別： 工程技術(shù)系
專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化
姓 名： 高一文
學(xué) 號(hào)： 05208301
2012 年 4 月 25 日
外文資料翻譯譯文
Microwave in walnut shell materials tensile mechanical properties of impact study
Abstract
Taking the picking fresh walnuts as the research object, the microwave walnut break hull test, break hull rate of 87.65%; And of microwave effects on the walnut shell materials tensile mechanical properties of influence, and the results showed that the microwave processing, walnut shell material elastic modulus, tensile strength and mechanical indexes and processing there were no significant changes before. In addition, also in walnut shell tensile mechanical properties of the tested and won the walnut the tensile strength of the place relict limit to 1. 47 M Pa, for sure walnut emerged inflationary pressure in microwave needed to provide the reference.
Keywords: microwave; Break hull; The whole shell tensile; Mechanical properties
0 Preface
Walnut machinery of the existence of high rate of broken emerged, the kernel rate is low has been restricted walnut realize mechanization production and processing of the important reason of our country, the development of walnut industrial caused certain influence. Therefore, explore new methods for realizing mechanization walnut emerged industrialization and export income, increase the economic benefit has urgent practical significance. At present, the technology for walnut mechanization emerged research focus on the gap emerged, blow for extrusion emerged, methods and the application of finite element method for related mechanical design emerged, but still has broken rate is high, the whole kernel rate low. In addition, the emerging technology used in the research is also emerged nuts is in the ascendant, such as YangRui etc in walnut laser irradiation behavior by the numerical analysis and simulation, explores the laser technology shelling mechanism; LiXiaoXia explores the buckwheat shell microwave method; ZhangLi, Yang fu Ephraim with microwave technology, realize the board of chestnut shell.
The author on the basis of previous studies, of microwave technology function mechanism of walnut emerged proposes that emerged walnut microwave method is feasible. This paper is to study this paper further discusses the front, to search for microwave processing technology parameters (power, time, humidity and temperature) in walnut shell material mechanics and the influence law of nature, studied the microwave technology role walnut shell material stretching before and after the mechanical properties of differences, and determine the seam walnut the tensile strength of the limit in, to determine the walnut microwave emerged inflationary pressure and further guidance for microwave technology parameters are selected to provide the reference.
1 Walnut microwave break hull test
Walnut is primarily through microwave microwave break hull role in walnutmeat, its internal water molecules in alternating under the influence of electromagnetic field polarization orientation for high frequency shift, the internal walnut in short time produce very high quantity of heat form high pressure water vapor, when water vapor pressure of the pressure of walnut is inflation pressure is greater than the ultimate tensile stress walnut, walnut burst. Therefore, the density of the nut shell is its internal structure formed an important guarantee of high pressure; The walnuts contain moisture is internally generated the material basis of high pressure water vapor; Microwave technology parameters (power, time and temperature, etc) is able to rupture external power of walnut. Therefore, it is necessary to walnut microwave technology needed to break hull parameters were tested.
1.1 materials and equipment
Test is just picked off cortical JinLong 1 cotton walnut as the research object, the walnuts moisture content of 21%, to prevent water loss, will test sample in a plastic bag sealed stored in the refrigerator for refrigeration.
W LD 07S--08 type glanze microwave ovens, microwave role, power and temperature are time adjustable; Vernier gauges.
1.2 test method
The three factors 3 level completely combination test, each portfolio selection three shape, size close of walnut similar as repeated samples. Before the test test walnut trunnion, diameter, caliper size. The end, observation and rupture of walnut recorded.
1.3results and analysis
Walnut microwave break hull situation as is shown in table 1.
Table 1 walnut microwave break hull test results
Group number
Temperature
Power∕W
Time∕min
Broken shell /%
1
50
300
2
100
2
50
300
3
66.7
3
50
300
4
33.3
4
50
500
2
100
5
50
500
3
100
6
50
500
4
66.7
7
50
700
2
100
8
50
700
3
66.7
9
50
700
4
100
10
60
300
2
66.7
11
60
300
3
66.7
12
60
300
4
100
13
60
500
2
100
14
60
500
3
100
15
60
500
4
100
16
60
700
2
100
17
60
700
3
100
18
60
700
4
66.7
19
70
300
2
66.7
20
70
300
3
100
21
70
300
4
100
22
70
500
2
100
23
70
500
3
66.7
24
70
500
4
100
25
70
700
2
100
26
70
700
3
100
27
70
700
4
100
From the table that 1, 81 a walnut, only 10 star have not broken open, break hull rate reached 87. 65%, if consider alone each temperature, each power, each time break hull rate, the result in table 2.
Table 2 single factor in walnut the influence of emerged rate
Factor
Temperature/
Power/w
Time/min
50
6
70
300
500
700
2
3
4
Broken shell /%
81.5
88.8
92.6
74.1
92.6
96.3
85.2
85.2
92.6
From the table 2, it is known that in the three factors, the temperature of high and low vapor pressure of the internal to the size of the size of the power to the internal temperature rise the speed of the water vapor; Because W LD 07S--08 type microwave equipment work characteristics, that is, to stop working after set temperature, so the length of time can not influence within the maximum pressure steam shell, will not affect the speed of temperature rise. So time to the influence of the factors emerged relatively small rate, and the results were consistent with the findings.
2 Microwave in walnut shell materials tensile mechanical properties of influence
Through to the walnut microwave before and after processing the contrast test that destructive compression, microwave treatment of walnut compression significantly less destructive power, this shows that on lots of walnut break hull, for in the microwave treatment not burst of walnut and compression is the easy emerged. In addition, we also found that the microwave process, walnut high pressure water vapor by the inside of the role, the tensile deformation happen. Therefore, the microwave technology in walnut shell materials tensile mechanical properties of influence, but for further reveal the mechanism of the walnut microwave emerged provides the basis. The author of such microwave before and after the shell material role elastic modulus and tensile strength comparison test.
2. 1 sample preparation
The test samples and in front of the experimental study of walnut emerged the same, with the saw in walnut along the axis direction for about 10 mm long, wide about 2 mm of walnut as specimens. Because walnut is curved shell form, had taken the length of the specimen should be as low as possible, in the direction of the small curvature of the better effect under saws. Will pass the microwave processing and without processing (control group) were made of walnut specimens, with caliper measured the length, width and thickness.
2. 2 equipment and methods
SAN S CMT 6140 microcomputer control electronic universal testing; Accuracy of 5% N 200 N sensor.
Set for 10 mm loading rate/m in, the routine material mechanics tensile test methods. Because of the specimen is too small, to avoid gripping broke when specimens or clip slanting, gripping use tweezers when operating. Record force deformation and fracture walnut of force value.
2. 3 results and analysis
Walnut shell materials tensile mechanical indexes such as test value shown in table 3.
From the table 3, it is known that the microwave processing get after the modulus of elasticity as walnut 21. 82 M P a, tensile strength of 10. 043 M Pa; Before the microwave processing elastic modulus is 22. 52 M Pa, tensile strength for 9. 57 MP a. microwave effects on the walnut shell that material has a little influence on tensile mechanical properties.
LiangLi etc: microwave in walnut shell materials tensile mechanical properties of impact study
Table 3 walnut shell materials tensile mechanical property index
Number
Length /mm
Width /mm
Thickness /mm
Area /mm2
Most strongly /N
Modulus of elasticity /Mpa
Tensile strength /Mpa
1
13. 60
1.90
1.38
2.62
20.34
24.20
7.76
Control
14. 26
2.56
1.70
4.35
40.42
4.00
9.29
2
10.68
2.00
1.48
2.96
29.54
27.70
9.98
Control
11.52
2.56
1.78
4.56
25.55
26.70
5.61
3
10.24
2.62
1.08
2.83
10.38
20.40
3.67
Control
14.96
1.80
1.70
3.06
10.76
7.03
3.52
4
16.30
3.58
1.98
7.09
77.26
3.59
10.90
Control
15.18
2.88
1.98
5.7
81.03
12.40
14.21
5
13.22
3.68
1.16
4.27
72.74
20.00
17.60
Control
14.82
3.20
2.00
6.4
38.63
17.20
12.84
6
16.66
3.92
1.48
5.8
91.26
12.40
12.87
Control
17.64
3.98
1.48
5.89
106.31
32.80
18.05
7
14.26
2.98
1.28
3.81
56.17
46.00
14.72
Control
13.84
3.32
2.14
7.1
84.70
18.30
11.92
8
14.96
2.00
1.78
3.56
62.56
11.90
17.57
Control
11.82
3.92
1.82
7.13
45.99
32.20
6.45
9
15.12
2.70
1.28
3.46
9.25
29.70
2.68
Control
10.78
3.00
1.72
5.16
56.59
17.10
10.97
10
14.56
2.44
1.88
4.59
12.30
22.30
2.68
Control
12.38
3.02
1.48
4.47
12.83
57.50
2.88
3 Walnut shell whole stretch mechanics performance is determined
Emerged from walnut microwave experimental results that, by all the breakdown of the sample after microwave processing are from walnut suture line the breakdown of the place, and it shows in walnut suture line tensile mechanical properties and surface of different materials walnut. Therefore, the need to place relict tensile mechanical nature of the study, this needs in walnut shell the tensile test. Because of walnut size is differ, irregular shape, test the clip if too loose, the tensile easily when slippage; If the clip too tight, it is easy to appear clip crack a phenomenon, so difficult test. For this reason, we designed a set of adjustable size shape walnut shell chuck for walnut shell of the tensile test.
3. 1 equipment and methods
Test in SAN S CMT 6140 microcomputer control electronic universal testing machine, a self-made walnut special jig. Before the test, will walnut and surface with a fixture acetone clean, and the determination of walnut trunnion, side diameter and diameter. The two clamping fixture first in the testing machine, adjust the fixture chuck size to appropriate value will chuck after fixed, again with strength and AB glue stick to the fixture will walnut (will show the seams of the walnut, do not stick on the glue) to try to ensure that the center of the two fixtures in one line, and walnut and the vertical seam lines. To glue dry after appearing again the walnut shell stretch mechanics performance test, the end of the shape of the cross section will walnut surveying and mapping out and record the most strong values.
3. 2 results and analysis
In walnut shell when the tensile, walnut seam place along the cracked. At this time, the stress in walnut suture line reaches limit, this stress value is measured by the testing machine of the most strongly and shifted walnut in circular seam for the calculation of the sectional area. Test results listed in table 4.
Table 4 walnut shell tensile test the test results
Serial number
Shaft Diameter /mm
Diameter /mm
Side diameter /mm
Shell thickness of suture /mm
Density of the suture line /( N﹒mm- 1)
Most strongly /N
Ultimate tensile strength of suture /MPa
1
30.70
30.46
30.98
5.16
7.17
685.70
1.44
2
30.00
31.30
38.20
1.98
2.85
279.64
1.40
3
35.82
38.00
39.50
6.24
8.27
985.99
1.64
4
38.58
32.36
30.76
4.50
6.27
636.77
1.45
5
33.00
34.80
33.20
4.59
4.28
467.73
1.11
6
33.82
34.02
34.14
2.26
3.80
406.26
1.81
The mean
33.67
33.49
34.46
4.10
5.44
577.02
1.47
From the table 4, it is known that the seam of walnut in limit tensile stress for 1. 47 MPa, and walnut on the surface tensile stress value 9. 57 MPa compared are much smaller, this is what walnut in microwave role in the cause of the broken seam after, this limit tensile stress can be used as microwave technology parameter selection basis.
4 Conclusion
Based on the test of fresh walnuts emerged, and walnut shell material and the mechanical properties of walnut shell are tested, get the following main conclusions:
(1) the fresh walnuts microwave process after the break hull rate can amount to 87. 65%, in the microwave technology parameters, temperature and power is the time factor to influence emerged rate.
(2) test after the microwave processing of walnut elastic modulus is 21. 82 MPa, tensile strength of 10. 043 M Pa, both with the processing there were no significant changes before that microwave role in walnut shell material has a little influence on tensile mechanical properties.
(3) test in the seam of walnut limit tensile stress value is 1. 41 MPa, and walnut shell material limit tensile stress value is much more than a small, for choosing suitable for microwave technology parameters of walnut emerged provides reference basis.
References:
[1] ShiJianXin, Michael essien moving army. Walnut kernel machinery at home and abroad and emerged from the present situation and the problem study [J]. J xinjiang agricultural mechanization, 2001 (6) : 29 32.
[2] Michael essien moving army. Walnut kernel methods and test emerged take [D]. Urumqi: xinjiang agricultural university, 2002.
[3]DongYuan DE, ShiJianXin, QiaoYuanYuan. Walnut different way of emerged emerged take effect benevolence [J]. Journal of agricultural products processing, 2007 (9) : 4 5, 9.
[4] ShiJianXin, ZhaoHaiJun, Michael essien moving army. Based on the finite element analysis technology of walnut shell [J]. Journal of agricultural engineering, 2005, 21 (1) : 185 188.
[5] WuZiYue. Cotton walnut shell take benevolence of mechanical [J]. Journal of agricultural engineering, 1995, 11 (4) : 164 169.
[6] YangRui, yan. Laser and walnut interaction is the mechanics and finite element analysis [J]. Agriculture machine research, 2008 (4) :.
[7] LiXiaoXia. Buckwheat shell mechanical properties and microwave process test emerged [D]. TaiGu: shanxi agricultural university, 2008.
[8] ZhangLi. Chestnut microwave device mechanism and processing technology research [D]. Hefei: hefei university of technology, 2004.
[9] Yang fu Ephraim, takami m, ZhuNiu. Use the microwave can related to the new technology of garments shell to new method [J]. Food science and technology, 2006 (9) : 80 83.
外文原文
微波對(duì)核桃殼體材料拉伸力學(xué)性質(zhì)的影響研究
摘 要
以剛采摘的新鮮核桃為研究對(duì)象，進(jìn)行了微波核桃破殼試驗(yàn)，破殼率達(dá)到87.5%，同時(shí)，研究了微波作用對(duì)核桃殼體材料拉伸力學(xué)性質(zhì)的影響，結(jié)果表明：微波處理后，核桃殼體材料彈性模量、抗拉強(qiáng)度等力學(xué)性質(zhì)指標(biāo)與處理前比較無(wú)明顯變化。另外，還對(duì)核桃整殼拉伸力學(xué)性質(zhì)指標(biāo)與處理前比較無(wú)明顯變化。另外，還對(duì)核桃整殼拉伸力學(xué)性質(zhì)進(jìn)行了測(cè)定獲得了核桃殼縫合線處的拉伸強(qiáng)度極限值為1.47MPa，為確定核桃微波破殼所需的膨脹壓力提供了參考依據(jù)。
關(guān)鍵詞：微波；破殼；整殼拉伸；力學(xué)性質(zhì)
0 前 言
核桃機(jī)械破殼存在的破碎率高、整仁率低等問(wèn)題一直是制約核桃實(shí)現(xiàn)機(jī)械化生產(chǎn)加工的重要原因, 對(duì)我國(guó)核桃產(chǎn)業(yè)的發(fā)展造成了一定影響。因此，探索新的機(jī)械化核桃破殼方法對(duì)于實(shí)現(xiàn)產(chǎn)業(yè)化、出口創(chuàng)匯、增加經(jīng)濟(jì)效益等具有迫切的現(xiàn)實(shí)意義。目前，國(guó)內(nèi)外對(duì)于核桃機(jī)械化破殼技術(shù)的研究主要集中在定間隙擠壓破殼、打擊破殼等方法及應(yīng)用有限元等方法進(jìn)行相關(guān)破殼機(jī)械的設(shè)計(jì)方面，但仍存在破碎率高、整仁率低等問(wèn)題。另外，將新興技術(shù)應(yīng)用于堅(jiān)果破殼的研究也是方興未艾，如楊銳等對(duì)核桃受激光輻照行為進(jìn)行了數(shù)值分析與模擬，探索了激光技術(shù)脫殼機(jī)理；李曉霞探索了蕎麥微波脫殼方法； 張莉、楊芙蓮等利用微波技術(shù)實(shí)現(xiàn)了對(duì)板栗的脫殼。作者在前人研究的基礎(chǔ)上，對(duì)微波技術(shù)進(jìn)行核桃破殼的作用機(jī)理進(jìn)行了初探，證明核桃微波破殼方法是可行的。本文是對(duì)前面研究的進(jìn)一步深入探討，為探求微波加工工藝參數(shù)(功率、時(shí)間、濕度和溫度)對(duì)核桃及殼體材料力學(xué)性質(zhì)的影響規(guī)律，試驗(yàn)研究了微波技術(shù)作用前后核桃殼體材料拉伸力學(xué)性質(zhì)的差異，并測(cè)定了核桃殼縫合線處的拉伸強(qiáng)度極限值，為確定核桃微波破殼所需的膨脹壓力并為進(jìn)一步指導(dǎo)微波技術(shù)參數(shù)的選擇提供參考依據(jù)。
1 核桃微波破殼試驗(yàn)
核桃微波破殼主要是通過(guò)微波作用于核桃仁時(shí)，其內(nèi)部水分子在交變電磁場(chǎng)作用下極化取向作高頻轉(zhuǎn)變，致使核桃殼內(nèi)部在短時(shí)間內(nèi)產(chǎn)生很高的熱量形成高壓水汽，當(dāng)高壓水汽對(duì)核桃殼的壓力即膨脹壓力大于核桃殼的拉伸極限應(yīng)力時(shí)，核桃殼發(fā)生破裂。因此，果殼的致密結(jié)構(gòu)是其內(nèi)部形成高壓的重要保證；核桃仁所含的水分是內(nèi)部產(chǎn)生高壓水汽的物質(zhì)基礎(chǔ)；微波的技術(shù)參數(shù)(功率、時(shí)間和溫度等)則是核桃殼能夠破裂的外在動(dòng)力。因此，有必要對(duì)核桃微波破殼所需的技術(shù)參數(shù)進(jìn)行試驗(yàn)研究。
1.1 材料與儀器
試驗(yàn)選用采摘后剛褪去外皮的晉龍1號(hào)棉核桃為研究對(duì)象，核桃仁含水率達(dá) 21% ， 為防止水分散失，將試驗(yàn)樣本用塑料袋密封置于冰箱內(nèi)藏，WLD07S-08 型格蘭仕微波爐，微波作用溫度、功率和時(shí)間均可調(diào)；游標(biāo)卡尺。
1.2 試驗(yàn)方法
采用3因素3水平完全組合試驗(yàn)，每個(gè)組合選取3個(gè)形狀相似、大小相近的核桃作為重復(fù)樣本，試驗(yàn)前測(cè)試核桃的軸徑、橫徑、測(cè)徑大小。試驗(yàn)結(jié)束時(shí)，觀測(cè)核桃殼破裂情況并進(jìn)行記錄。
1.3 結(jié)果與分析
核桃微波破殼情況如表 1所示。
表 1 核桃微波破殼試驗(yàn)結(jié)果
組號(hào)
溫度/℃
功率∕w
時(shí)間∕min
破殼率 /%
1
50
300
2
100
2
50
300
3
66.7
3
50
300
4
33.3
4
50
500
2
100
5
50
500
3
100
6
50
500
4
66.7
7
50
700
2
100
8
50
700
3
66.7
9
50
700
4
100
10
60
300
2
66.7
11
60
300
3
66.7
12
60
300
4
100
13
60
500
2
100
14
60
500
3
100
15
60
500
4
100
16
60
700
2
100
17
60
700
3
100
18
60
700
4
66.7
19
70
300
2
66.7
20
70
300
3
100
21
70
300
4
100
22
70
500
2
100
23
70
500
3
66.7
24
70
500
4
100
25
70
700
2
100
26
70
700
3
100
27
70
700
4
100
由表 1可知，81顆核桃中只有10顆未破開(kāi)，破殼率達(dá)到 87. 65% ，若單獨(dú)考慮每個(gè)溫度、每個(gè)功率、每個(gè)時(shí)間的破殼率，其結(jié)果見(jiàn)表 2。
表 2 單因素對(duì)核桃破殼率的影響
因素
溫度/℃
功率/w
時(shí)間/min
50
6
70
300
500
700
2
3
4
破殼率/%
81.5
88.8
92.6
74.1
92.6
96.3
85.2
85.2
92.6
由表 2可知, 在這 3個(gè)因素中，溫度的高低決定殼體內(nèi)的水蒸汽壓力的大小；功率的大小決定殼體內(nèi)水蒸汽溫度上升的快慢；由于WLD07S-08型微波設(shè)備的工作特點(diǎn)，即達(dá)到設(shè)定溫度后就停止工作，故時(shí)間的長(zhǎng)短不能影響殼體內(nèi)水蒸汽的最大壓力，也不影響溫度上升的快慢，所以時(shí)間因素對(duì)破殼率的08型微波設(shè)備的工作特點(diǎn)，即達(dá)到設(shè)定溫度后就停止影響相對(duì)較小，與前期研究結(jié)果一致。
2 微波對(duì)核桃殼體材料拉伸力學(xué)性質(zhì)的影響
通過(guò)對(duì)核桃微波處理前后壓縮破壞力的對(duì)比試驗(yàn)得知，微波處理后核桃的壓縮破壞力明顯減少，這說(shuō)明在進(jìn)行大量核桃破殼時(shí)，對(duì)于在微波處理后未發(fā)生破裂的核桃再進(jìn)行壓縮破殼是比較容易的。另外，我們還發(fā)現(xiàn)微波作用過(guò)程中，核桃殼受到內(nèi)部高壓水汽的作用，發(fā)生了拉伸變形。因此，研究微波技術(shù)對(duì)核桃殼體材料拉伸力學(xué)性質(zhì)的影響， 可為進(jìn)一步揭示核桃微波破殼的作用機(jī)理提供依據(jù)。作者對(duì)微波作用前后殼體材料的彈性模量及抗拉強(qiáng)度進(jìn)行了對(duì)比試驗(yàn)研究。
試驗(yàn)所用樣本與前面核桃破殼試驗(yàn)研究中相同，用鋸條在核桃上沿軸線方向獲取長(zhǎng)約10mm，寬約 2 mm的核桃殼作為試件。因?yàn)楹颂沂乔鷼ば蔚模≡嚰拈L(zhǎng)度應(yīng)盡量小，在曲率越小的方位鋸下的效果越好。將經(jīng)過(guò)微波處理和未經(jīng)處理(對(duì)照組)的核桃均制成試件，用游標(biāo)卡尺測(cè)取其長(zhǎng)度、寬度和厚度。
2.2 設(shè)備及方法
SANS-CMT 6140微機(jī)控制電子萬(wàn)能試驗(yàn)，精度達(dá)5%N的200N傳感器。設(shè)定加載速率為10mm/min，采用常規(guī)材料力學(xué)拉伸試驗(yàn)方法進(jìn)行。由于試件太小，為避免夾持時(shí)弄斷試件或夾歪，夾持時(shí)使用鑷子操作。記錄力變形曲線以及核桃殼發(fā)生破裂時(shí)的力值。
2.3 結(jié)果與分析
由表3可知，得到微波處理后核桃殼的彈性模量為21.82M P a，抗拉強(qiáng)度為10. 043 MPa；微波處理前彈性模量為22. 52MPa，抗拉強(qiáng)度為9.57MPa。說(shuō)明微波作用對(duì)核桃殼體材料的拉伸力學(xué)性質(zhì)影響不大。
表 3 核桃殼體材料拉伸力學(xué)性質(zhì)指標(biāo)值
編號(hào)
長(zhǎng)度 /mm
寬度/mm
厚度 /mm
面積 /mm2
最大力 /N
彈性模量 /Mpa
抗拉強(qiáng)度/Mpa
1
13. 60
1.90
1.38
2.62
20.34
24.20
7.76
對(duì)照
14. 26
2.56
1.70
4.35
40.42
4.00
9.29
2
10.68
2.00
1.48
2.96
29.54
27.70
9.98
對(duì)照
11.52
2.56
1.78
4.56
25.55
26.70
5.61
3
10.24
2.62
1.08
2.83
10.38
20.40
3.67
對(duì)照
14.96
1.80
1.70
3.06
10.76
7.03
3.52
4
16.30
3.58
1.98
7.09
77.26
3.59
10.90
對(duì)照
15.18
2.88
1.98
5.7
81.03
12.40
14.21
5
13.22
3.68
1.16
4.27
72.74
20.00
17.60
對(duì)照
14.82
3.20
2.00
6.4
38.63
17.20
12.84
6
16.66
3.92
1.48
5.8
91.26
12.40
12.87
對(duì)照
17.64
3.98
1.48
5.89
106.31
32.80
18.05
7
14.26
2.98
1.28
3.81
56.17
46.00
14.72
對(duì)照
13.84
3.32
2.14
7.1
84.70
18.30
11.92
8
14.96
2.00
1.78
3.56
62.56
11.90
17.57
對(duì)照
11.82
3.92
1.82
7.13
45.99
32.20
6.45
9
15.12
2.70
1.28
3.46
9.25
29.70
2.68
對(duì)照
10.78
3.00
1.72
5.16
56.59
17.10
10.97
10
14.56
2.44
1.88
4.59
12.30
22.30
2.68
對(duì)照
12.38
3.02
1.48
4.47
12.83
57.50
2.88
3核桃整殼拉伸力學(xué)性能的測(cè)定
從核桃微波破殼試驗(yàn)結(jié)果看出，所有經(jīng)微波處理后破裂的試樣均是從核桃縫合線處破裂的，這說(shuō)明核桃縫合線處的拉伸力學(xué)性質(zhì)與核桃殼表面材料的有所不同。因此，需要對(duì)縫合線處的拉伸力學(xué)性質(zhì)進(jìn)行研究，這就需要對(duì)核桃整殼進(jìn)行拉伸試驗(yàn)。由于核桃大小不一，形狀不規(guī)則，試驗(yàn)時(shí)若將其夾得太松，則拉伸時(shí)容易滑脫；若夾得太緊，則易出現(xiàn)夾裂現(xiàn)象，所以試驗(yàn)難度較大。為此，我們專門(mén)設(shè)計(jì)了一套可調(diào)節(jié)尺寸的殼形核桃?jiàn)A頭來(lái)進(jìn)行核桃整殼的拉伸試驗(yàn)研究。
3.1 設(shè)備與方法
試驗(yàn)在 SANSCMT6140微機(jī)控制電子萬(wàn)能試驗(yàn)機(jī)上進(jìn)行，采用自制的核桃專用夾具。 試驗(yàn)前，將核桃和夾具表面用丙酮清洗干凈，并測(cè)定核桃的軸徑、側(cè)徑和橫徑，將兩個(gè)夾具先裝夾在試驗(yàn)機(jī)上，調(diào)節(jié)夾具夾頭尺寸至合適值后將夾頭固定，再用強(qiáng)力AB膠將核桃粘到夾具上(將核桃的接縫露出,不可粘上膠)，盡量保證兩個(gè)夾具的中心在一條線上，且使核桃的縫合線與該中心線垂直。待膠完全干透后再進(jìn)行核桃整殼拉伸力學(xué)性能測(cè)試，試驗(yàn)結(jié)束時(shí)將核桃斷面的形狀測(cè)繪出來(lái)并記錄最大力值。
3.2 結(jié)果與分析
在進(jìn)行核桃整殼拉伸時(shí)，核桃沿縫合線處裂開(kāi)。此時(shí)，核桃縫合線處的應(yīng)力達(dá)到極限值，該應(yīng)力值是通過(guò)試驗(yàn)機(jī)上測(cè)出的最大力與裂開(kāi)后核桃縫合線處的環(huán)形截面積計(jì)算得到的，測(cè)試結(jié)果列于表4。
表4 核桃整殼拉伸試驗(yàn)測(cè)試結(jié)果
序號(hào)
軸徑 /mm
橫徑/mm
側(cè)徑 /mm
縫合線處殼厚/mm
縫合線密度/( Nmm-1)
最大力 /N
縫合線處極限拉伸應(yīng)力/MPa
1
30.70
30.46
30.98
5.16
7.17
685.70
1.44
2
30.00
31.30
38.20
1.98
2.85
279.64
1.40
3
35.82
38.00
39.50
6.24
8.27
985.99
1.64
4
38.58
32.36
30