Improving the reliability of visual inspections conducted by environmental health and safety professionals, on a hyperscale data centre construction site

The conduct of visual inspections on construction sites is of crucial importance for workplace safety. This is because visual inspection is the primary method by which construction site hazards are routinely observed, monitored and controlled. However, there is no consensus guidance as to how such visual inspections should be conducted. This is resulting in many observable hazards going unseen and therefore not being appropriately managed on construction sites worldwide. In an attempt to improve the reliability of visual inspection, this study presents results from an innovative method called systematic visual inspection which utilises an iterative set eye scan pattern during observation. In this study using one construction site, systematic visual inspection is compared with custom and practice visual inspections conducted by four environmental health and safety professionals (EHSPs) and four senior site managers. The results were as follows; the lead investigator who used the systematic visual inspection method observed a mean 37.70 hazards per inspection (SD=40.92). In sharp contrast, the mean number of observable hazards identified by EHSPs per inspection was 11.94 (SD=13.51). For site managers, the results were 10.87 per inspection (SD=12.40). This improvement in hazards observed by the use of the systematic visual inspection method was highly significant (p

A computational multiscale model for anisotropic failure of sheet molding compound composites

We present a holistic multiscale approach for constructing anisotropic criteria describing the macroscopic failure of sheet molding compound composites based on full-field simulations of microscale damage evolution. We use an anisotropic damage model on the microscale that directly operates on the compliance tensor, captures matrix and bundle damage via dedicated stress-based damage criteria and allows for a comparison of simulation and experimental results. To identify the damage material-parameters used in the non-linear and time-consuming full-field simulations, we utilize Bayesian optimization with Gaussian processes. We validate the full-field predictions on the microscale and subsequently identify macroscopic failure criteria based on distributions taken from experimental findings. We propose failure surfaces in stress space and stiffness-reduction triggered failure surfaces to cover both a structural analysis and a design process perspective

Direct Bundle Simulation approach for the compression molding process of Sheet Molding Compound

The manufacturing process of Sheet Molding Compounds (SMC) induces a reorientation of fibers during the flow, which influences local properties and is of interest for structural computations. Typically, the reorientation is described with an evolution equation for the second order fiber orientation tensor, which requires a closure approximation and multiple empirical parameters to describe long fibers. However, CT scans of SMC microstructures show that fiber bundles stay mostly intact during molding. Treating hundreds of fibers in such a bundle as one instance enables direct simulation on component scale. This work proposes a direct simulation approach, in which bundle segments experience Stokes’ drag forces and opposing forces are applied to the fluid field. The method is applied to specimens with a double-curved geometry and compared to CT scans. The Direct Bundle Simulation provides increased accuracy of fiber orientations and enables prediction of fiber-matrix separation with affordable computational effort at component scale

On the applicability of thermoforming characterization and simulation approaches to glass mat thermoplastic composites

Chopped fiber composite materials offer the potential to be used for complex geometries, including local thickness changes, ribs and beads, offering significant potential for functional lightweighting. Depending on the initial mold coverage and flowability of the material, the processing behaves either more like a compression molding or a thermoforming process. The latter is applicable to high initial mold coverages and includes typical thermoforming defects such as local wrinkling. Such defects are not predictable by conventional compression molding simulation approaches usually adopted for this material class. Therefore, thermoforming characterization and simulation approaches and their applicability to glass mat thermoplastic (47 vol.% long glass fiber, Tepex Flowcore) for high initial mold coverages is investigated. Abaqus in combination with several user-subroutines is applied. Valid material characterization results from torsion bar and rheometer bending tests are obtained and applied to an automotive structure in thermoforming simulation. Results indicate that the high stiffness and high viscosity captured by the rheometer bending test at low shear-rates are necessary to reproduce the wrinkling behavior observed in the experimental results. Discrepancy is most likely reducible to thermomechanical effects, and that the modelling approach does not account for thickness deformation due to transverse compression

Спермопродуктивність баранів-плідників породи тексель залежно від періоду сезонної активності та режиму використання

The results of laboratory studies of freshly obtained and deep-frozen semen of Texel breeding rams in the non-mating and mating periods under different modes of using 4, 6, and 8 ejaculates per week are given. It has been proven that during the non-mating period, when receiving four ejaculates per week compared to 6 and 8 ejaculates, the ejaculate volume was 11.3 and 22.6 % higher, respectively. The sperm concentration in it was 5.1 and 12.2 %, sperm activity was higher by 1.7 and 3.2 %, and their resistance by 7.1 and 17.3 percent. In the mating period under the above regimen, the ejaculate volume was 9.9 and 19.7 % higher; sperm concentration was 4.1 and 5.9 % higher; sperm activity was higher by 5.7 and 8.3 %, resistance was higher by 7 .7 and 19.9 percent. Higher quality indicators were found in the mode of obtaining four ejaculates after sperm cryopreservation in both research periods, on average, according to the activity of deconserved sperm by 3.2 and 8.0 and 5.8 and 11.2 %, freezing resistance by 0.7 and 2,0 and 2.6 and 4.6 %, survival by 7.6 and 15.5 and 2.2 and 10.6%, absolute survival rate by 3.4 and 8.1 and 4.7 and 8.5 percent Based on the analysis of the investigated indicators of freshly obtained and de-preserved sperm, it was experimentally confirmed that in the mating period compared to the non-mating period, they were significantly higher on average in freshly obtained sperm from 7.7 to 40.1 %, in cryopreserved sperm – from 2.9 to 16.7 percent. The preservation of acrosomes of sperm in the non-mating and mating period, when receiving four ejaculates per week compared to receiving 6 and 8, was higher by periods by 3.5 and 6.0 %, and 2.5 and 5 %, respectively. The studies established significantly higher quantitative and qualitative indicators of freshly collected and deconserved sperm in both seasonal activity periods under the regime of obtaining four ejaculates per week from breeding rams. Under this regime, the sperm is biologically complete, and its quality indicators meet the requirements of the instructions for the artificial insemination of sheep.Наведено результати лабораторних досліджень свіжоодержаної і глибокозамороженої спермии баранів-плідників породи тексель у непарувальний і парувальний періоди за різних режимів їх використання 4, 6 і 8 еякулятів за тиждень. Доведено, що у непарувальний період за режиму одержання 4 еякуляти за тиждень порівняно із 6 і 8 еякулятами об’єм еякуляту був більшим відповідно на 11,3 і 22,6 %, концентрація сперміїв у ньому на 5,1 і 12,2 %, активність сперміїв вищою на 1,7 і 3,2 %, їх резистентність на 7,1 і 17,3 %. У парувальний період за вищевказаного режиму об’єм еякуляту був більшим на 9,9 і 19,7 %, концентрація сперміїв на 4,1 і 5,9 %, активність сперміїв вищою на 5,7 і 8,3 %, резистентність на 7,7 і 19,9 %. Вищі якісні показники виявлені за режиму одержання 4 еякуляти після кріоконсервування сперми у обидва досліджуванні періоди в середньому за активністю деконсервованих сперміїв відповідно на 3,2 і 8,0 та 5,8 і 11,2 %, стійкістю до заморожування на 0,7 і 2,0 та 2,6 і 4,6 %, виживаністю на 7,6 і 15,5 та 2,2 і 10,6 %, показника абсолютного виживання на 3,4 і 8,1 та 4,7 і 8,5 відсотка. За аналізу досліджуваних показників свіжоодержаної і деконсервованої сперми експериментально підтверджено, що у парувальний період порівняно з непарувальним вони були значно вищими в середньому у свіжоодержаній спермі від 7,7 до 40,1 %, у кріоконсервованій – від 2,9 до 16,7 %. Збереженість акросом сперміїв у непарувальний і парувальний період, за отримання 4 еякуляти в тиждень порівняно з одержанням 6 і 8, була вищою відповідно за періодами на 3,5 і 6,0 % та 2,5 і 5 %. Проведеними дослідженнями встановлено значно вищі кількісні та якісні показники свіжоодержаної і деконсервованої сперми в обидва періоди сезонної активності за режиму одержання від баранів-плідників 4 еякуляти за тиджень. За такого режиму сперма є біологічно повноцінною, і її якісні показники відповідають вимогам інструкції зі штучного осіменіння овець

Injection molding of glass fiber reinforced polypropylene composite foams with laminate skins

Sandwich panels which consist of discontinuous glass fiber reinforced polypropylene composite foam core and continuous glass-fiber reinforced polypropylene laminate skins were manufactured using industry-scale equipment in a streamlined manner. The process included the two stages: (1) continuous glass-fiber reinforced polypropylene laminates as the face skins were produced using an automated tape layup machine and a hydraulic press and (2) discontinuous glass-fiber reinforced polypropylene composite as the core was foam injection-molded onto the face laminates (i.e., overmolding) with a physical blowing agent, nitrogen. The results suggested that the addition of the laminate skins and foaming by the core-back (or mold opening) technique can greatly reduce weight of material needed to have the same bending stiffness and maximum bending force