邱述金，原向陽(yáng)，郭玉明，崔清亮，武新慧，張志勇

品種及含水率對(duì)谷子籽粒力學(xué)性質(zhì)的影響

邱述金1，原向陽(yáng)2，郭玉明1，崔清亮1※，武新慧1，張志勇1

（1. 山西農(nóng)業(yè)大學(xué)工學(xué)院，太谷 030801；2. 山西農(nóng)業(yè)大學(xué)農(nóng)學(xué)院，太谷 030801）

谷子籽粒群是具有黏彈性性質(zhì)的生物材料，谷子加工儲(chǔ)藏和機(jī)械收獲等作業(yè)環(huán)節(jié)需考慮其黏彈性，該文研究了不同品種、不同含水率對(duì)谷子籽粒群黏彈性力學(xué)指標(biāo)的影響。該試驗(yàn)以不同品種、不同含水率為試驗(yàn)因素，以谷子籽粒群的瞬時(shí)彈性模量、遲滯彈性模量、松弛時(shí)間和黏度系數(shù)為試驗(yàn)指標(biāo)進(jìn)行蠕變?cè)囼?yàn)，并對(duì)試驗(yàn)結(jié)果進(jìn)行方差分析。結(jié)果表明：谷子籽粒群的蠕變特性可由四元件Burgers模型描述，不同含水率、不同品種谷子籽粒群的蠕變參數(shù)各異。品種對(duì)谷子籽粒群的遲滯彈性模量影響顯著，晉谷21號(hào)谷子籽粒群的遲滯彈性模量均值為0.609 3 MPa，顯著高于張雜10號(hào)的0.522 2 MPa。含水率對(duì)谷子籽粒群的瞬時(shí)彈性模量、遲滯彈性模量和黏度系數(shù)影響均顯著，均呈隨含水率升高而降低的趨勢(shì)，含水率為12.10%的谷子籽粒群的瞬時(shí)彈性模量0.752 6 MPa顯著高于含水率為16.05%的0.613 6 MPa和20.00%的0.569 7 MPa，含水率為12.10%、16.05%、20.00%的谷子籽粒群的遲滯彈性模量分別為0.706 4、0.583 5、0.407 5 MPa，含水率為12.10%的谷子籽粒群的黏度系數(shù)1 234.7 MPa·s顯著高于20.00%的796.8 MPa·s，含水率對(duì)谷子籽粒群的松弛時(shí)間影響不顯著。該文通過(guò)試驗(yàn)研究了不同品種和不同含水率的谷子籽粒群的蠕變特性，為谷子低損收獲、加工儲(chǔ)藏及參數(shù)優(yōu)化提供了理論支持。

含水率；力學(xué)性能；模型；谷子籽粒群；蠕變特性；品種

0 引 言

谷子是中國(guó)丘陵山地有機(jī)旱作農(nóng)業(yè)重要的雜糧作物之一[1]，其機(jī)械收獲與加工生產(chǎn)過(guò)程中持續(xù)受到復(fù)雜外力的作用，比如聯(lián)合收獲機(jī)攪龍輸送過(guò)程中谷子籽粒群受持續(xù)推進(jìn)力的作用，運(yùn)輸儲(chǔ)藏環(huán)節(jié)中的隨機(jī)碰撞等機(jī)械作用會(huì)導(dǎo)致谷子種子破裂、胚胎受損等問(wèn)題[2]。谷子籽粒群的流變學(xué)特性是相關(guān)裝備研發(fā)、工藝制定的理論基礎(chǔ)，可為低損收獲、低損加工、低損儲(chǔ)藏等提供新的思路及參數(shù)優(yōu)化。

目前，國(guó)內(nèi)外學(xué)者對(duì)農(nóng)業(yè)物料的流變學(xué)特性研究已經(jīng)取得了較大進(jìn)展。梁麗等[3]研究了小麥莖稈流變性質(zhì)，建立了為小麥優(yōu)種指標(biāo)評(píng)價(jià)流變模型。Ma等[4]研究了麥麩膳食纖維對(duì)小麥面團(tuán)的流變學(xué)指標(biāo)影響，結(jié)果表明添加麥麩膳食纖維后降低了面團(tuán)的黏彈性應(yīng)變極限，但機(jī)械強(qiáng)度得到增強(qiáng)。宮澤奇[5]結(jié)合流變學(xué)參數(shù)研究了青貯玉米秸稈螺旋致密成型工藝，建立了2個(gè)經(jīng)典Maxwell模型并聯(lián)的應(yīng)力松弛模型，獲得螺旋致密成型物料應(yīng)力松弛規(guī)律。盛韶陽(yáng)[2]研究了不同含水率玉米籽粒的黏彈性，得到蠕變過(guò)程玉米籽粒的應(yīng)變隨含水率增加而增大，松弛過(guò)程玉米籽粒的應(yīng)力隨含水率增加而減小的結(jié)論。嚴(yán)平宇等[6]利用機(jī)械動(dòng)態(tài)熱分析儀對(duì)水稻種子進(jìn)行了流變特性研究，建立了水稻種子的五元件開(kāi)爾文模型和三元件麥克斯韋模型。還有其他學(xué)者研究了大豆[7]、豌豆等作物的流變學(xué)特性，獲得了碰撞損傷及籽粒應(yīng)力開(kāi)裂的影響規(guī)律[8]。針對(duì)小籽粒谷物的流動(dòng)特性[9]、摩擦特性運(yùn)動(dòng)學(xué)[10-11]、作物莖稈、種子及其加工產(chǎn)品面粉等的流變特性的研究較多[12-13]。程緒鐸等[14]曾指出國(guó)內(nèi)糧倉(cāng)堆高大、儲(chǔ)藏溫度高、含水率大、時(shí)間久會(huì)使大豆彈性變小。馬小愚等[15]通過(guò)應(yīng)力松弛試驗(yàn)，得到不規(guī)則形狀的大豆、小麥種子的擠壓方程，提出了可識(shí)別松弛參數(shù)的Z變換法。張洪霞[16]對(duì)稻米及米飯籽粒進(jìn)行了應(yīng)力松弛試驗(yàn)，獲得了應(yīng)力松弛指標(biāo)，建立了力學(xué)指標(biāo)隨影響因素變化的回歸方程。還有學(xué)者應(yīng)用有限元分析方法研究物料流變特性，如王芳等[17-18]利用有限元法仿真研究了西瓜的力學(xué)特性，驗(yàn)證了仿真數(shù)值解的可行性；藏楠[19]用ANSYS對(duì)馬鈴薯的力學(xué)特性進(jìn)行仿真，仿真結(jié)果較好地反應(yīng)馬鈴薯的蠕變特性。

我們團(tuán)隊(duì)前期對(duì)谷子單個(gè)籽粒的靜態(tài)力學(xué)特性[20-21]、谷子莖稈力學(xué)特性[22-23]及谷子葉片摩擦特性[24-25]等方面進(jìn)行了研究，在此基礎(chǔ)上研究不同含水率的谷子籽粒群的蠕變特性，獲取不同品種、不同含水率谷子籽粒群在聯(lián)合收獲機(jī)收獲、輸送及儲(chǔ)藏等過(guò)程的蠕變參數(shù)，為谷子等雜糧作物的低損機(jī)械收獲、加工、儲(chǔ)藏及參數(shù)優(yōu)化等提供理論依據(jù)。

1 試驗(yàn)材料和方法

1.1 試驗(yàn)材料

本試驗(yàn)所用谷子取自山西農(nóng)業(yè)大學(xué)谷子試驗(yàn)田，品種為晉谷21號(hào)和張雜10號(hào)，這些品種大面種植于山西乃至全國(guó)，具有較強(qiáng)的代表性。考慮谷子貯藏、加工時(shí)的含水率為10%～13%，谷子收獲時(shí)的含水率約為18%～20.00%，合理劃分谷子的含水率，分別為12.10%、16.05%、20.00%。為配置不同含水率的谷子籽粒群，用精度為0.01g的分析天平對(duì)谷子籽粒群稱質(zhì)量。含水率為16.05%、20.00%的樣品需要分2次進(jìn)行，期間每隔兩個(gè)小時(shí)需要均勻搖晃。配水的過(guò)程在塑封袋中完成，將處理好的樣品密封，放入冷藏箱中備用，試驗(yàn)前將樣品拿出恢復(fù)至室溫。按式（1）配置含水率。

式中為所需配水的質(zhì)量，g；為谷子籽粒群的質(zhì)量, g；1為谷子籽粒群的初始含水率，%；2為需要調(diào)配后的含水率，%。

將谷粒試樣稱質(zhì)量，準(zhǔn)確至0.01 g，并將試樣放入溫度為105 ℃的干燥箱中干燥4.5 h，時(shí)間到后打開(kāi)干燥箱將樣品立即蓋上盒蓋，取出稱質(zhì)量，記錄數(shù)據(jù)，再放入干燥箱中干燥0.5 h，時(shí)間到后重復(fù)上述操作，若質(zhì)量差小于0.02 g，則認(rèn)為谷子干燥完成。計(jì)算含水率，重復(fù)3次取其平均值。含水率按式（2）進(jìn)行計(jì)算。

式中為含水率，%；為初始鮮質(zhì)量，g；為最后干質(zhì)量，g。

1.2 試驗(yàn)方法

試驗(yàn)采用CMT-6104型萬(wàn)能試驗(yàn)機(jī)，設(shè)計(jì)加工了用于谷子籽粒群流變特性試驗(yàn)的專用夾具，如圖1所示，加載壓頭采用圓柱壓頭，壓頭直徑為100 mm。試驗(yàn)前進(jìn)行預(yù)試驗(yàn)以了解谷子籽粒群在保證不脫殼、不破殼的前提下所能承受的最大載荷。蠕變?cè)囼?yàn)參數(shù)設(shè)置為：試驗(yàn)方向?yàn)閴合?，力控?0.0 N/s，目標(biāo)力控制4 000 N，力保載900 s，試驗(yàn)結(jié)束后不自動(dòng)返車，測(cè)定應(yīng)變與時(shí)間關(guān)系。

圖1 谷子籽粒群蠕變?cè)囼?yàn)夾具

1.3 理論基礎(chǔ)

楊明韶等[26-28]認(rèn)為，農(nóng)業(yè)物料中的大多數(shù)是黏彈性體，可分為線性黏彈性體和非線性黏彈性體，目前尚未有成熟的研究支持用非線性黏彈性理論解釋農(nóng)業(yè)物料的流變特性，為簡(jiǎn)化模型，本文擬采用四元件Burgers模型研究谷子籽粒群的蠕變特性，如式（3）所示。

式中()為蠕變過(guò)程中時(shí)刻的應(yīng)變，為蠕變時(shí)間，s，0為施加的恒定應(yīng)力，MPa；0為瞬時(shí)彈性模量，MPa；E為遲滯彈性模量，MPa；為黏滯系數(shù)，MPa·s，τ為延遲時(shí)間，s。

2 結(jié)論與分析

試驗(yàn)獲得了應(yīng)力保持為0.127 MPa下的谷子籽粒群的蠕變特性曲線，根據(jù)公式（3），采用本質(zhì)非線性回歸方法計(jì)算蠕變參數(shù)，用SAS軟件擬合不同品種、不同含水率的谷子籽粒群Burgers蠕變模型[29-30]，結(jié)果如表1所示。

表1 Burgers蠕變模型擬合參數(shù)

注：數(shù)據(jù)采用3次重復(fù)取平均值±標(biāo)準(zhǔn)偏差的形式。

Note: Data were averaged in the form of triplicates ± standard deviation.

2.1 品種對(duì)蠕變參數(shù)的影響

晉谷21號(hào)、張雜10號(hào)蠕變?cè)囼?yàn)的應(yīng)變-時(shí)間關(guān)系曲線如圖2所示。

谷子籽粒群蠕變曲線表明，在試驗(yàn)開(kāi)始至設(shè)定載荷過(guò)程中，谷子籽粒群的應(yīng)變隨載荷的增加呈線性增長(zhǎng)的趨勢(shì)，在應(yīng)力保持階段谷子籽粒群的應(yīng)變隨時(shí)間的增加緩慢增大，不同品種的谷子籽粒群蠕變曲線有差異。

為研究品種對(duì)蠕變特性參數(shù)的影響，本文選取0.05作為顯著性檢驗(yàn)標(biāo)準(zhǔn)[26]，對(duì)試驗(yàn)數(shù)據(jù)進(jìn)行方式分析，結(jié)果如表2所示。

注：圖中jg21代表晉谷21號(hào)，zz10代表張雜10號(hào)，下同。

表2 不同品種谷子籽粒群蠕變參數(shù)的比較

注：同一列數(shù)據(jù)后不同字母表示數(shù)據(jù)間有顯著差別（<0.05），下同。

Notes: Values in the column with different superscripts were significantly different (<0.05) , the same below.

不同品種的谷子籽粒群的方差分析結(jié)果表明：品種對(duì)于谷子籽粒群遲滯彈性模量的影響顯著，顯著性值為0.023 3，晉谷21號(hào)谷子籽粒群的遲滯彈性模量均值為0.609 3 MPa，顯著高于張雜10號(hào)的0.522 2 MPa。遲滯彈性模量表征了谷子籽粒群的硬度，即晉谷21號(hào)谷子籽粒群的硬度高于張雜10號(hào)，決定系數(shù)為0.994 6，分析結(jié)論可靠；品種對(duì)谷子籽粒群的瞬時(shí)彈性模量、松弛時(shí)間和黏度系數(shù)影響不顯著。

2.2 含水率對(duì)蠕變參數(shù)的影響

含水率分別為12.10%、16.05%、20.00%的谷子籽粒群蠕變?cè)囼?yàn)的應(yīng)變-時(shí)間關(guān)系曲線如圖3所示。

為研究含水率對(duì)蠕變特性參數(shù)的影響，本文選取0.05作為顯著性檢驗(yàn)標(biāo)準(zhǔn)[26]，對(duì)試驗(yàn)數(shù)據(jù)進(jìn)行方式分析，結(jié)果如表3所示。

不同含水率的谷子籽粒群的方差分析表明：含水率對(duì)瞬時(shí)彈性模量影響顯著，顯著性值達(dá)0.047 3，瞬時(shí)彈性模量隨含水率升高而減小，在0.05水平上，含水率為12.10%的谷子籽粒群的瞬時(shí)彈性模量0.752 6 MPa顯著高于含水率為16.05%的0.613 6 MPa和20.00%的0.569 7 MPa，決定系數(shù)為0.968 2，說(shuō)明分析結(jié)論可靠；含水率對(duì)遲滯彈性模量影響顯著，顯著性值為0.006 1，隨含水率升高，遲滯彈性模量降低，含水率為12.10%、16.05%、20.00%的谷子籽粒群的遲滯彈性模量分別為0.706 4、0.583 5、0.407 5 MPa，決定系數(shù)為0.994 6；含水率對(duì)谷子籽粒群的黏度系數(shù)影響較顯著，含水率為12.10%的谷子籽粒群的黏度系數(shù)1 234.7 MPa·s顯著高于20.00%的796.8 MPa·s，隨含水率升高，黏度系數(shù)降低，決定系數(shù)為0.935 3；含水率對(duì)谷子籽粒群的松弛時(shí)間影響不顯著。

圖3 不同含水率的谷子籽粒群蠕變曲線圖

表3 不同含水率谷子籽粒群蠕變參數(shù)比較

瞬時(shí)彈性模量和遲滯彈性模量分別表征谷子籽粒群的彈性和硬度，隨谷子籽粒群含水率的升高，其瞬時(shí)彈性模量和遲滯彈性模量降低，導(dǎo)致蠕變曲線高度增加，籽粒群的應(yīng)變隨之增加。

3 結(jié) 論

本文通過(guò)試驗(yàn)研究了不同品種、不同含水率的谷子籽粒群的流變特性，結(jié)果表明：

1）對(duì)晉谷21號(hào)和張雜10號(hào)2個(gè)品種的谷子籽粒群進(jìn)行了蠕變?cè)囼?yàn)，擬合獲得蠕變模型參數(shù)，并以四元件Burgers模型描述了谷子籽粒群的蠕變行為。

2）不同品種、不同含水率的谷子籽粒群均可采用Burgers研究其蠕變特性，但其流變學(xué)參數(shù)各異。品種對(duì)谷子籽粒群的遲滯彈性模量影響顯著，晉谷21號(hào)谷子籽粒群的遲滯彈性模量高于張雜10號(hào)。含水率對(duì)谷子籽粒群的瞬時(shí)彈性模量、遲滯彈性模量和黏度系數(shù)影響均顯著，均呈隨含水率升高而降低的趨勢(shì)。

本研究為谷子等農(nóng)業(yè)松散物料的儲(chǔ)藏、加工、收獲及運(yùn)輸?shù)忍峁┲匾睦碚撘罁?jù)，影響農(nóng)業(yè)物料流變性能的因素較多，除含水率和品種的影響外，還與溫度、物料的內(nèi)部分子結(jié)構(gòu)及化學(xué)成分組成等眾多因素相關(guān)，農(nóng)業(yè)松散物料的流變特性還需要結(jié)合生命科學(xué)原理進(jìn)一步深入研究。

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Effects of variety and moisture content on mechanical properties of millet

Qiu Shujin1, Yuan Xiangyang2, Guo Yuming1, Cui Qingliang1※, Wu Xinhui1, Zhang Zhiyong1

(1.,,030801; 2.,,030801,)

In order to clarify the rheological mechanical properties of millet grain group during mechanical harvesting and processing, this paper studied the effects of different varieties and different moisture contents on the creep characteristics of millet grain group. In this experiment, different varieties (Jingu 21, Zhangza 10), and different moisture contents (12.10%, 16.05%, 20.00%) of millet grain group were selected as creep experimental factors. The creep characteristics (instantaneous elastic modulus, delayed elastic modulus, relaxation time and viscosity coefficient) of millet seed group were used as experimental indicators, and one-way analysis of variance and multi-factor analysis of variance were performed. Based on the original contents of millet seed group, the target moisture contents of the millet grain group were formulated to be 12.10%, 16.05%, 20.00%. The experiment was conducted on the CMT-6104 universal testing machine, and the special fixture for testing the creep characteristics of millet grain group was designed. Combining the Burgers model, nonlinear programming method was used to optimize search regression parameters, and creep parameters of millet grain group were obtained. The creep curve of millet grain group of different varieties showed that, as time going on, the amount of deformation caused by creep tended to be constant, which reaching the strain saturation. There were differences in the millet grain group creep characteristic curves of the different varieties. The significance test standard was 0.05, and the variance analysis was performed. The results showed that the creep characteristics of millet grain group could be described by the four-element Burgers model, and the creep parameters of millet grain group with different moisture content and different varieties were different. The variety had a significant effect on the delayed elastic modulus of the millet grain group. The delayed elastic modulus of the Jingu 21 millet grain group was higher than that of Zhangza 10. The moisture content had significant effects on the instantaneous elastic modulus, delayed elastic modulus and viscosity coefficient of the millet grain group, which was decreasing while the moisture increasing. The instantaneous elastic modulus of the millet grain group with the water content of 12.10% was significantly higher than the water content of 16.05% and 20.00%. The delayed elastic modulus of the millet grain group with the moisture content of 12.10% was significantly higher than the water content of 20.00%. The instantaneous elastic modulus and the delayed elastic modulus represented elasticity and hardness of the millet grain group, respectively. With the increasing of the moisture content of the millet grain group, the instantaneous elastic modulus and the delayed elastic modulus of millet grain group decreased, resulting in a high increasing of the creep curve. The strain in the screw conveyor of combine harvester was correspondingly larger. In this paper, the creep properties of millet grain group with different varieties and different moisture contents were studied experimentally, which provided theoretical support for low-loss harvesting, processing and storage and parameter optimization of millet. There are many factors affecting the mechanical properties of the material, in addition to the influence of moisture contents and varieties, it is also related to many factors such as temperature, internal molecular structure and chemical composition of the material, et al. The rheological properties of agricultural materials need to be further studied in conjunction with the principles of life sciences.

moisture content; mechanical properties; model; millet grain group; creep characteristics; variety

邱述金，原向陽(yáng)，郭玉明，崔清亮，武新慧，張志勇. 品種及含水率對(duì)谷子籽粒力學(xué)性質(zhì)的影響[J]. 農(nóng)業(yè)工程學(xué)報(bào)，2019，35(24)：322－326. doi：10.11975/j.issn.1002-6819.2019.24.038 http://www.tcsae.org

Qiu Shujin, Yuan Xiangyang, Guo Yuming, Cui Qingliang, Wu Xinhui, Zhang Zhiyong. Effects of variety and moisture content on mechanical properties of millet[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(24): 322－326. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.2019.24.038 http://www.tcsae.org

2019-07-28

2019-11-27

“十三五”國(guó)家重點(diǎn)研發(fā)項(xiàng)目（2016YFD0701801）；國(guó)家現(xiàn)代農(nóng)業(yè)產(chǎn)業(yè)體系（CARS-06-13.5-A28）；山西農(nóng)業(yè)大學(xué)博士科研啟動(dòng)項(xiàng)目（2015YJ01）；晉中市科技重點(diǎn)研發(fā)計(jì)劃（Y182013）

邱述金，副教授，博士，主要從事農(nóng)業(yè)物料機(jī)械特性與農(nóng)業(yè)機(jī)械化裝備研究。Email：sxauqsj@sina.com

崔清亮，教授，博士，主要從事農(nóng)業(yè)物料機(jī)械特性與農(nóng)業(yè)機(jī)械化裝備研究。Email：qlcui@126.com

10.11975/j.issn.1002-6819.2019.24.038

S183

A

1002-6819(2019)-24-0322-05