Thin-walled tubes play a significant role in increasing the energy absorption in energy absorbing systems. Holed thin-walled tubes are a suitable option for use in these systems due to the ease of production and the lack of geometry complexity. In this paper, a new geometric pattern for holed thin-walled cylindrical tubes made of aluminum alloy 6061 is presented, to improve the energy absorption characteristics. To this aim, the Taguchi design of experiment method has been used to find the optimal levels of the geometrical parameters of the tube to achieve the maximum energy-to-weight ratio and the minimum effective equivalent strain. The number of rows of holes, the number of holes in each row, the diameter of the small hole and the diameter coefficient of the small hole were considered as the geometric (input) parameters of the tubes. The initial crushing force, the total absorbed energy, the ratio of energy to weight and the ratio of the maximum initial force to the average force were compared for the optimal layouts. Examining the results showed that the arrangement of the holes in the middle with 3 rows of holes, 8 holes in each row, diameter of the small hole of 5 mm and the diameter coefficient of 1.2 (the large diameter is 6 mm) will lead to the best energy absorption result.

Introduction & The mental foramen is a part of lower jaw which has neurovascular bundles and also is important in biology. 3D imaging of this area by cone beam computed tomography (CBCT) before surgery can prevent some problems. This study aims to evaluate the anatomic position and geometrical shape of the mental foramen by CBCT images In this research, the CBCT images (by NewTom and Planmeca promax 3D set) of 85 patients referred to dentistry school clinic or other clinics in Hamadan city were studied. These patients did not have their first and second premolar teeth extracted in both right and left sides. The geometrical shape of mental foramen, the canal angle connecting to mental foramen compared to the buccal plate of lower jaw, distance from the lower border of mental foramen to the lower border of lower jaw, position of mental foramen relating to the root of adjacent tooth and the incidence of accessory mental foramen were studied. The means of canal angle connecting to mental foramen in the right side in men and women were 123.3 and 130.1 and in the left side were 123.8 and 133.7, respectively. The mean distance from the lower border of mental foramen to the lower border of lower jaw in the right side in men and women were: 12.4 and 13.3 mm and in the left side were: 12.7 and 13.6 mm, respectively. Also, there is a meaningful statistical relation between gender and the angle of canal of mental foramen, regarding to the buccal plate in both sides. Regarding to the variations in the position and shape of mental foramen and the angle connecting to the mental foramen related to the buccal plate and accessory mental foramen, investigation of CBCT images before placement of implants is necessary.

In recent years, laser drilling is used as a new process for micro drilling with high precision, less time and high aspect ratio in various industries, particularly in the aerospace industry. To improve the quality of drilling process, identification of the process parameters and investigation of their influence on the output characteristics are necessary. In present study, laser percussion drilling process was performed on Hastelloy X nickel-based superalloy and the effect of process parameters including laser frequency, pulse width and laser beam keeping time was investigated on the hole geometry characteristics (hole entrance and exit diameter, hole entrance and exit circularity and hole taper). The results indicate that by increasing the laser frequency, hole entrance and exit diameter increases but hole entrance and exit circularity and hole taper decrease. By increasing the pulse width, hole entrance and exit diameter increases but hole entrance and exit circularity decreases. Also, with increasing the pulse width, hole taper decreases. When the laser beam keeping time increases, hole entrance and exit diameter increases but hole entrance and exit circularity and hole taper decrease.

Bone drilling is a common procedure in orthopedics. During the bone drilling process, heat is generated, which can lead to cell death and consequently alter the mechanical properties of the bone. Additionally, the surface quality of the drilled area changes depending on the drilling parameters, which can significantly affect the healing period, treatment success, and the patient's pain experience. This study aims to identify the drilling process parameters that influence the surface quality of bone drilling to approach minimally invasive surgery. The rotational speed, feed rate, and tool diameter in the drilling process affect the bone temperature and axial force, impacting the surface quality. In this research, fresh femur bone from a 3-year-old cow with a cortical bone thickness of 9–11 mm in the diaphysis was used. Based on the findings of this study, it is recommended that a rotational speed of 50 rpm, a feed rate of 50 mm/min, and a tool diameter of 2.5 mm be used during the drilling process to reduce cracking and surface roughness in the drilled area.

In the present research, the mixed-mode fracture mechanics analysis in a plate with central hole under tensile loading is considered. It is assumed that a plate containing two symmetrical hole-edge cracks is bonded with two dissimilar planes. The stress intensity factors at the crack tips are calculated. The problem is modeled in Casca software and this model is analyzed with Franc software. The effects of various factors such as hole diameter, crack length, angle of crack and material properties of plates have been investigated on stress intensity factors. The stress intensity factors increases with increasing crack length. Also, the stress intensity factors increases with the increase of hole diameter. For a certain amount of for small crack lengths the effect of cracks length on variation of stress intensity factors is more than the hole diameter but for large crack lengths the effect of hole diameter on variation of stress intensity factors is more than the cracks length.

The use of perforated plates in the impact of projectiles reduces damage to the main target, the final cost of construction and surface density. The purpose of this paper is to present a new and complete analytical model to obtain the penetration depth as well as the deflection of the rigid head projectile after hitting the perforated plate. This model is based on the development of the model provided by Chen, and in the following experimentally investigation of the impact of the projectile on the perforated plate has been paid. for this purpose For this purpose, projectiles of AISI 52100 and perforated plates of AISI 1045 with 3 hole diameters of 5, 7 and 9 mm have been used. Finally, the results obtained from the analytical solution are compared with the experimental results and the accuracy of the analytical model is proved. After examining the different states of impact, it can be seen that the projectile deviates from its path after hitting the hole and changes from vertical impact to oblique impact. As the diameter of the hole or the amount of overlap of the projectile with the hole increases, the deflection of the projectile also increases.‎

The cold roll forming is one of the common processes to form metal profiles in the industry. Due to the nature of the bending deformation in cold roll forming process, spring-back is one of the most important defects. In order to compensate the spring-back, the amount of spring-back must be correctly predicted. In this article, the effect of the hole and its position on the spring-back has been investigated by experimental and numerical methods. three channel section profiles made of St12 and thickness of 1 mm, without hole, with circular holes on the bend area and with holes on the flange were used. Cold roll forming was done in three stations with a fixed bending radius pattern with 15 degree bending in each forming station and numerical solution using Abaqus finite element software. The results indicate that there is a relationship between the amount of spring-back and the position of the hole in such a way that the amount of spring-back in hole on the bend area profile is 9% more than the hole-less profile and in hole on the flange profile is 16% less than hole-less profile. Also, according to finite elements results, it was observed that the amount of equivalent strain in the bend area of the profile with holes on the bend area is 20% less and in the profile with holes near the bend area is 16% more than the profile without holes, which can justify the difference observed in the amount of spring-back.

In this research، effects of different factors in the CNC machine through- Hole boring of MDF and particleboard were investigated. Variables in boring were selected bit diameter in 3 levels 5،10 and 15 mm، feed speed in 2 levels 0. 3 m/min and 0. 6 m/min and rotary speed of machine axis in 3 levels 300،1500 and 3000 rmp. The goal of this study was to measure effects of mentioned factors on edge- quality of through- holes made in particle- board and MDF. Results have shown that with all bit diameters used، increasing rotary speed of bit improves smoothness of holes in both sides and boring dusts turned to finer sizes. Increasing feed speed did show positive effect on edge surface quality and lowered burr formation.

Today, the application of materials such as glass has been widely developed in the manufacture of micronutrients, electronics and medical equipment because of its high hardness, chemical resistance and high abrasion. But due to high hardness and low toughness, mechanical machining can not be applied. The Electrochemical discharge method is a new machining method that is capable of machining hard and non-conductive electrical materials such as glass. In the process of electrochemical discharge drilling, the dimensional accuracy of the hole and especially its inlet area is important. but almost, the inlet of the hole has a high slope, which leads to excessive hole overcut and tapering of the hole side wall. In this study, to remove the high slope entrance area, a thin intermediate part was used which will be separated from the main workpiece after the drilling process. The results showed that mentioned method reduced the entrance overcut of the hole by 50 to 76% depending on the diameter of the tool. Also, the hardness measuring of points on the hole inlet showed that using the intermediate part led to the smaller heat-affected zone (HAZ) around the hole entrance.

This study was carried out to investigate the morphology of the oval foramen in the fetal stage of dromedary camel fetuses by routine dissection. The hearts were obtained from 21 fetuses that were collected from Yazd slaughter house of Iran. The Crown Vertebral Rump Length (CVRL) of fetuses were from 10.1 to 85 cm and estimated gestational age calculated from 81.9 to 270 days old. The results showed that anatomical structures of oval foramen in fetal camels concluded of septum primum (valve of oval foramen), foramen secundum, septum secundum and a large passageway called oval foramen (foramen ovale). The septum primum was a flat, long thin, white color and unfenestrated membrane (fold) in all fetuses. The thin fold was in the lower portion of formen secundum and constituted about %75 to %100 of the lumen of the oval foramen in the small to large fetuses, respectively. So, it constituted a large proportion of lumen and was large enough to cover the opening of oval foramen, specialy in large fetuses. The septum secundum was a thick, short and crescent-shaped fold above of ovale foramen. The oval foramen showed like an oval passage way between free border and arms of septum secundum. It was concluded that despite of size of heart and oval foramen, all structural arrangements of heart oval foramen in fetus of camel are similar to reports about other mammals and human.