Impact of Excitation and Material Parameters on the Efficiency of Ultrasonic Cutting of Bakery Products

ABSTRACT: Cutting with tools excited by ultrasound is increasingly applied in the food industry, especially for cheese, confectionary, and bakery products. Due to the lack of a thorough understanding of the separation process, most of the ultrasonic cutting systems are designed and applied on the basis of empirical knowledge. The aim of the study was to elaborate the impact of ultrasonic parameters, that is, amplitude and frequency, on the cutting process, and special emphasis was placed on resulting effects in the close vicinity of the cutting edge, which are reflected by the separation forces. To allow a direct investigation of the mechanical separation without artifacts due to secondary effects such as melting and cavitation, the crumb of different bakery products (for example, dark and white bread, yeast dumplings, and cake) were analyzed. The results show that the influence of ultrasonic amplitude and frequency can be expressed by the maximum vibration speed on the cutting edge. For each product, an increasing maximum vibration speed results in a particular reduction of the cutting force and an increased quality of the cut. The magnitude of the cutting force reduction is inversely related to a material-specific parameter c_x, which was calculated from the mechanical properties according to the speed-of-sound concept. Therefore, the determination of c_x allows a specific adjustment of ultrasonic amplitude and frequency to achieve optimum cutting quality.     

Ultrasonic cutting of foods with inclined moving blades

Cutting with devices excited by ultrasound is a promising alternative to conventional cutting when the materials contain particles which differ in stiffness and elasticity from the surrounding bulk or when they consist of layers which exhibit largely differing mechanical properties. Aim of the present study was to evaluate the impact of ultrasonic excitation and blade inclination (slice-to-push ratio) on cutting forces and cutting work of different foods with a fast-moving device which was excited in a way that the direction of vibration was parallel to the edge of the blade. The results show that ultrasonic excitation significantly reduces cutting force, that the magnitude of cutting force reduction largely depends on the product, and that cutting force and cutting work increase with increasing cutting velocity. Whereas these interactions are because of the micro-saw movement of the cutting tool, it was not possible to explain the product-dependent response to blade inclination.     

Ultrasonic cutting of cheese: Composition affects cutting work reduction and energy demand

Eight cheese varieties with different moisture (357–488 g kg^?1), fat (183–335 g kg^?1) and protein content (202–292 g kg^?1) were subjected to ultrasonic cutting using a 40 kHz guillotine sonotrode. Cutting force curves were evaluated with respect to ultrasound-induced cutting work reduction and energy demand of the sonotrode. With cutting velocity and ultrasonic amplitude set to 2500 mm min^?1 and 12 μm, respectively, composition had a significant effect on the response of the cheeses. Whereas cutting work reduction was mainly determined by fat-in-dry matter, the energy demanded by the sonotrode to maintain vibration was inversely interrelated to the ratio of moisture to solids-non-fat. Three selected cheeses were subjected to cutting experiments with systematically varied cutting velocity and amplitude. The results indicate that the cheeses respond differently to the cutting parameters, and that their careful adjustment is helpful for a target-orientated design of the process.     

Assessment of the antibacterial activity of a triclosan-containing cutting board

Several studies have shown that consumers may not clean cutting boards properly between preparation of raw and cooked meat. Cutting boards may therefore act as sources for contamination of cooked meat or other ready-to-eat foods with pathogenic and spoilage bacteria. The aim of the work was to investigate if cutting boards containing the antimicrobial compound triclosan can reduce the viability of bacteria, thus acting as a hygiene barrier. Survival and growth of food pathogens and spoilage bacteria on two cutting boards without antimicrobials and a commercial cutting board containing triclosan were tested. No difference in bacterial counts on cutting boards without and with triclosan was found after exposure to naturally contaminated chicken filets for one hour. Pathogenic and spoilage bacteria were inoculated on coupons (6.7-7 log per coupon) of cutting boards and incubated at 25 °C at controlled relative humidity for 24 and 72 h. At a relative humidity of 100%, growth of Escherichia coli, Salmonella, Staphylococcus aureus, coagulase-negative staphylococci (CNS) and Serrratia spp. was observed and no antibacterial effect of the triclosan-containing board was found except for against Listeria monocytogenes. At lower humidity (70% RH) less growth was found on the triclosan-containing cutting board than untreated boards after 24 h. After 72 h of incubation, cell counts were reduced on triclosan-containing boards, with the most pronounced antibacterial effects observed against Salmonella, S. aureus and CNS. For S. aureus and Salmonella it was found that when a lower initial cell count was applied (3.5 log per coupon), the triclosan-containing board had an antibacterial effect under humid conditions, as well as a more pronounced antibacterial effect under dry conditions.An agar overlay assay showed that triclosan migrated out of the coupons. Repeated washing of the triclosan-containing cutting boards reduced the antibacterial effect, thus the amount of triclosan available on the surface seemed to be limited. In conclusion, using triclosan-containing cutting boards as a hygienic barrier may only work under certain conditions (low humidity, long exposure time, and clean conditions) and not against all genera of bacteria.     

蛋糕分切插纸一体机的设计与研究

针对蛋糕分切过程中出现的蛋糕局部坍塌、破损和残渣粘刀等问题,设计了一款以超声波切割刀为核心装置的蛋糕分切插纸一体机。该机包括超声波切割装置、蛋糕插纸装置和控制系统等关键机构,通过控制系统设置超声波切割刀振动频率、蛋糕旋转台转盘速度和蛋糕分切等分数等参数,进而实现不同类型、不同需求蛋糕的分切插纸,一次性完成蛋糕分切和插纸两道工序,并解决了蛋糕坍塌、破损和粘刀等问题。     

硅片切割技术的现状和发展趋势

随着太阳能技术和半导体技术的飞速发展,对硅片的直径,厚度和精度提出了更高的要求,传统的硅片加工方式已经不能满足需要。文章分析内圆切割、多线切割、电火花钱切割和超声振动切割四种硅片切割方式,指出多线切割是硅片的主要切割方式,电火花线切割硅片技术有很大的发展潜力,超声振动切割优于其它三种硅片切割方式。     

微凹版涂布单元振动测试与分析

本研究采用现代测试分析技术对涂布机的微凹版涂布单元进行振动测试分析,通过测试比较微凹版辊操作侧和传动侧的垂直方向和水平方向在不同频率下的振动现象,说明垂直方向的振动比同侧的水平方向振动大,操作侧的振动比同方向传动侧的振动大.墙板传动侧水平方向和垂直方向振动加速度的测试数据,说明在低频率阶段,垂直方向的加速度大于水平方向;当运转频率大于2Hz时,水平方向的加速度大于垂直方向的加速度.本研究为微凹版涂布单元结构及抗震设计提供参考.     

果冻食品高速双面贴标机伺服系统主振频率研究

建立全自动果冻食品高速双面贴标机伺服系统的动力学模型,得出伺服系统的等效转动惯量和等效综合刚度;借助于伺服系统动力学方程,求得伺服系统的传递函数和主振频率;通过根轨迹图和系统振动稳定L(ω)曲线,指出提高系统传动刚度、削减工作机构惯性和惯性元件的失动量或提高阻尼,可以削弱谐振烈度;采用校正网络和综合贴标贴膜速度反馈亦可减弱谐振。     

Energy balance of the orthogonal cutting process

The objectives of this research were to estimate energy quotas during orthogonal machining of medium density fiberboard (MDF), to investigate the extent to which input energy is utilized during pure cutting, and to determine how much energy is dissipated in other unintentional phenomena which accompany the machining process. The effects of cutting speed and feed rate on the energy balance were also investigated. The experimental results show that effectiveness of the cutting process mostly depends on the efficiency of the electric motor. Cutting efficiency decreases dramatically when the load on the electric motor is less than 50% of the nominal torque. The amount of pure cutting energy increases significantly with increasing cutting speed. Cutting efficiency reaches 68% under machining at a cutting speed of 30 m/s. The most significant undesirable phenomenon accompanying orthogonal cutting is thermal output, which can reach 28% of the input energy. Values for vibrational and noise energy emitted during machining of MDF are insignificant.     

胸部位移与文胸舒适性关系初探

为考察胸部位移与舒适性之间的关系,设计一组实验。分别以裸体、穿着3/4文胸和穿着运动文胸状态于5 km/h和10 km/h的跑速在跑步机上跑步,用VICON运动学测量分析系统捕捉测试者各轴向上的胸部位移值,并要求测试者对各状态下的文胸舒适性进行主观评价。结果发现,跑速与胸部位移正相关;胸部位移与舒适感负相关,垂直轴向上的波幅是影响舒适性的主要因素;对比三种穿着状态,运动文胸能够限制胸部垂直方向上的位移,改善胸部舒适性。本文为文胸舒适性的客观评判提供了一种可行的方法。     

环形金刚石线锯切割大理石试验研究

选用环形电镀金刚石线锯切割大理石,分析了锯丝线速度、工件进给速度和锯丝张紧力对大理石表面加工质量的影响,研究了金刚石锯丝的磨损机理。结果表明：工件进给速度对大理石表面粗糙度的影响最大,锯丝线速度对大理石表面粗糙度的影响次之,锯丝张紧力对大理石表面粗糙度的影响再次之。在本试验参数范围内,最优工艺参数为：工件进给速度为10mm/min,锯丝线速度为30m/s,锯丝张紧力为100N。     

包装容器内粉体的振动密实过程分析与数值模拟

研究振动对粉体包装容器内粉体密实的影响。基于离散单元的理论知识,对粉体在不同振幅和频率下的振动密实过程进行仿真。对不同振幅和频率影响下,颗粒X方向上的速度进行分析。在其他条件一定的情况下,随着振幅和频率的增加,颗粒X方向上的速度波动变大,且振幅对颗粒速度波动的影响不显著。这说明基于离散元法的数值模拟可使粉体的振动密实过程清晰可见,振动参数的分析对粉体包装工艺的改进提供了有意义的依据。     

象鼻子收线机振动分析及稳定性改进

采用机械动力学理论分析象鼻子收线机振动原因。结构设计不合理是引起振动和制约收线速度的首要因素。改进结构设计的措施:(1)增大支承轴承间距与尾端轴承距拨盘之间距离之比,提高系统一阶临界转速,增强抗振能力;(2)减少激振源,减轻激振强度。可采取改进静平衡方式减小偏心激振和改减速箱减速传动为大带轮减速传动的方法。以600卷筒的收线机为例,一次改进后,收线机运行速度提高28%,二次改进后,收线机运行速度比改进前提高63%,可在650 m/min速度下平稳运行,有效提高了象鼻子收线机的运行速度和系统稳定性。     

Studies of the main cutting force at and near a cutting edge

The present work is a study of how various parameters affect the cutting forces at, and near a cutting edge when cutting wood at full speed and with all cutting edges of the tool. Statistical methods from experimental results are used to develop a model.     

切削参数对竹材切削力影响的研究

研究了竹材切削不同刀具前角、切削量与切削速度对切削力的影响.刀具前角对主切削力的影响较为显著,随刀具前角的增大,所需主切削力明显减小.主切削力与切削量成正相关关系.切削速度对切削力的影响不大.     

A bioinspired setup to evaluate food graininess via tactile friction and vibration

Current tribological methods show unsatisfactory performance in evaluating food graininess, neglecting the existence of tactile vibration in human oral perception. Inspired by this biological mechanism, we proposed a novel setup that can mimic the oral tactile sensation. Taking chocolate syrups and barley grass gels as model foods, feasibility tests show our setup capable of acquiring the tactile friction and vibration information. The optimal acquisitions are obtained at the sliding speed of 0.5 mm/s and normal force of 200 mN. Simultaneously, friction coefficient and the vibration amplitude at the frequency of 24 Hz (on Y-axis) are extracted as the feature parameters. Results show that the vibration amplitude is more informative than the friction coefficient in discriminating graininess levels, and integrating both feature parameters can improve the discrimination performance. By unveiling the importance of tactile vibration, this study paves the way for developing new food texture analyzers based on tactile sensing techniques.     

基于动力学有限元分析的实木地板损伤检测

介绍了脉冲锤击法检测实木地板损伤及测定其动态弹性模量的理论依据,并通过有限元模拟与试验验证了其可行性。试验结果表明：脉冲锤击法能有效地测得实木地板的固有频率与动态弹性模量,所得动态弹性模量值比静态弹性模量值稍大;测试中,拾振点应选择在主振频率振型的最大振幅处或其附近区域,激振点应选择在离拾振点较远且振幅较大的区域;固有频率可对实木地板的损伤程度进行较好的判定。     

DRYING of COFFEE BERRIES IN A VIBRATED TRAY DRYER OPERATED WITH SOLIDS RECYCLE and SINGLE‐STAGE1

A vibrated tray dryer was tested for drying coffee berries. It consists of a vertical chamber (0.33 m × 0.18 m × 1.30 m) provided with four trays. the trays are supported by a vibrated shaft. Experimental tests were carried out at a vibration amplitude of 1 mm and at a variable frequency. the process itself consisted of feeding the vibrated tray dryer with an initial mass of coffee berries: after leaving the dryer through the discharge channel, the berries were fed again to the top of the dryer by a bucket elevator (intermittent operation with recycle of the coffee berries). Drying tests were carried out with drying air velocity of 2.4 m/s. the drying air control temperature was related with the temperature of the coffee berries at the discharge (under 45C). the drying time required for coffee berries to reach 12.6% (wb) moisture was 28 h, initial mass (moisture of 67% wb) was 5.54 kg. In this work the influence of vibration in single‐stage drying is also shown. the single‐stage operation shows that vibration (besides promoting the conveyance of coffee berries) also reduces the time of drying.     

蔗糖溶液中超声空化泡运动数值的模拟

为了解超声场作用下,蔗糖溶液中空化泡动力学的影响因素及影响规律,运用Rayleigh-Plesset方程模拟空化泡运动过程.结果表明:空化泡的振幅随着超声波频率增大而减小;随着超声波声强的增大而增大,空化变易;随着环境压力增大而减小,空化变难;随着空化泡初始半径增大而减小,空化强度变弱;随蔗糖溶液温度增大而增大,空化强度加大;随蔗糖溶液浓度增大而减小,空化强度减小.研究还发现,双频超声作用的空化效果比单频超声作用时强.     

PcBN刀具硬态干切削条件对切屑形貌的影响

通过对PcBN刀具硬态干切削GCr15轴承钢的试验研究,观察分析研究了不同切削条件对切屑形貌的影响。结果表明,随着切削速度的增加,切屑锯齿化程度也越高,当切削速度大于200m/min时,切屑类似于挤裂状;随着进给量的增加,切屑的锯齿化程度越来越明显,且在进给量达到0.5mm/r时,切削产生严重变形;随着背吃刀量的增加,切屑的卷曲程度越大,但对锯齿化影响并不大,但当背吃刀量为0.05mm时,切削基本呈带状。