Re: [Vo]:Question regarding basic solid mechanics and one directional applied stress
Hi This is a traditional basic question in solid mechanics and there is nothing special with it. I am interested in the earth crust and bore holes in it. Gravity is causing vertical stress on the crust but it is not obvious if the horizontal stress is positive or negative. One problem is if the crust can expand sideways and thus have a horizontal stress or if the geometry only allows isotropic contraction as would be the case if a sphere is shrinking. If we assume a negative horizontal stress what would the stress be around a vertical hole in the ground? The radial stress on the surface of the hole would be zero so there would be a gradient on the radial stress from the surface and into the rock which is identical to a volumetric force. Volumetric forces cause adiabatic heat gradients which means the measured temperature in the bore hole is different from that in the rock deeper into the walls of the hole. In order to calculate this non heat conducting (adiabatic) heat gradient I need to know the potential function of the displacement of the atoms in the crystals. Since silicon dioxide is the dominant component of the crust I will focus on such crystals. There is a bore hole in Poland where the temperature is dropping with increasing depth. This would indicate a positive horizontal stress. It can not be explained with the dominant theory of heat conduction from the interiors of the earth. David On Sun, May 4, 2008 at 11:25 PM, R C Macaulay [EMAIL PROTECTED] wrote: Howdy David, A brain teaser question. The answer is yes if you accept that expansion and contraction actually occurs depending on the materials of the cylinder. Mention of the cylinder being solid presents another teaser. Certain solids react to being stressed. Predictive science of materials is become the cutting edge technology whereas in the past we used empirical tests alone. LIke non-invasive quality control tests, predictive science is what the Russians face in discovering what is happening with their Soyuv space capsule re-entry problems. You may be working on that task so I wish you well. You may set up a testing method of proving that the stress caculated is indeed negative by building a sorta makeshift air comparison picnometer of a version used for density measurement of dry drilling mud. Fun stuff. Richard - Original Message - *From:* David Jonsson [EMAIL PROTECTED] *To:* vortex-l@eskimo.com *Sent:* Sunday, May 04, 2008 3:36 PM *Subject:* [Vo]:Question regarding basic solid mechanics and one directional applied stress Hi If I put a wheight on a vertical cylinder it will be shortened and its radius will be somewhat increased. I wonder if the radial increase is considered a negative stress in radial direction? Is the stress tensor something like this? -a 0 0 T= 0 0 0 0 0 b Where a and b are positive values and the coordinates are cylindrical *ρ*, *φ*, *z* (ISO 31-11). David -- David Jonsson Sweden phone callto:+46703000370
Re: [Vo]:Question regarding basic solid mechanics and one directional applied stress
Howdy David, I don't know the answer. Are we discussing earth science and soil mechanics separate from solid mechanics? Nobody knows earth science except geologists and Al Gore and they know it all. Just ask one of them. Soil mechanics is a less than exact science and the approach you have toward examining the stresses based on temperature may lead you astray. Sound interesting. Some astute geologists at Houston Texas may have more information . You may try the University of Houston since they are near to the center of the geologists in the petro business. Years ago I was did some work on gas measurement in west Texas involving CO2 icing together with a witches brew of H2S. acid, etc. and down hole pressure exceeding 10k PSIG. Across Texas we find anomalies in down hole temperatures. Near surface temperatures may be 140 degrees F and drop as depth increases and suddlenly increase above 200 F. An interesting study was done on a well near Brazoria Texas. An exploratory well was drilled to a final depth of 19-20k feet deep with no success. Gosh awful pressures and problems with heat and salt water intrusion from nearby Gulf of Mexico.You may try to chase this report down at Mobil Oil. They seem to be having a problem with down hole temperature in the nation of Chad. Exxon has some production there. The Chinese are moving in where the bullets don't fly. Their biggest problem in production seems to be lightning and electric submersible pump motors in the oilwells. We looked at the problem from a lightning arrestor view and decided there was not a solution because of the soil. Strange and weird stuff. Richard David Jonsson wrote, This is a traditional basic question in solid mechanics and there is nothing special with it. I am interested in the earth crust and bore holes in it. Gravity is causing vertical stress on the crust but it is not obvious if the horizontal stress is positive or negative. One problem is if the crust can expand sideways and thus have a horizontal stress or if the geometry only allows isotropic contraction as would be the case if a sphere is shrinking. If we assume a negative horizontal stress what would the stress be around a vertical hole in the ground? The radial stress on the surface of the hole would be zero so there would be a gradient on the radial stress from the surface and into the rock which is identical to a volumetric force. Volumetric forces cause adiabatic heat gradients which means the measured temperature in the bore hole is different from that in the rock deeper into the walls of the hole. In order to calculate this non heat conducting (adiabatic) heat gradient I need to know the potential function of the displacement of the atoms in the crystals. Since silicon dioxide is the dominant component of the crust I will focus on such crystals. There is a bore hole in Poland where the temperature is dropping with increasing depth. This would indicate a positive horizontal stress. It can not be explained with the dominant theory of heat conduction from the interiors of the earth. David
[Vo]:Question regarding basic solid mechanics and one directional applied stress
Hi If I put a wheight on a vertical cylinder it will be shortened and its radius will be somewhat increased. I wonder if the radial increase is considered a negative stress in radial direction? Is the stress tensor something like this? -a 0 0 T= 0 0 0 0 0 b Where a and b are positive values and the coordinates are cylindrical *ρ*, * φ*, *z* (ISO 31-11). David -- David Jonsson Sweden phone callto:+46703000370
Re: [Vo]:Question regarding basic solid mechanics and one directional applied stress
Howdy David, A brain teaser question. The answer is yes if you accept that expansion and contraction actually occurs depending on the materials of the cylinder. Mention of the cylinder being solid presents another teaser. Certain solids react to being stressed. Predictive science of materials is become the cutting edge technology whereas in the past we used empirical tests alone. LIke non-invasive quality control tests, predictive science is what the Russians face in discovering what is happening with their Soyuv space capsule re-entry problems. You may be working on that task so I wish you well. You may set up a testing method of proving that the stress caculated is indeed negative by building a sorta makeshift air comparison picnometer of a version used for density measurement of dry drilling mud. Fun stuff. Richard - Original Message - From: David Jonsson To: vortex-l@eskimo.com Sent: Sunday, May 04, 2008 3:36 PM Subject: [Vo]:Question regarding basic solid mechanics and one directional applied stress Hi If I put a wheight on a vertical cylinder it will be shortened and its radius will be somewhat increased. I wonder if the radial increase is considered a negative stress in radial direction? Is the stress tensor something like this? -a 0 0 T= 0 0 0 0 0 b Where a and b are positive values and the coordinates are cylindrical ρ, φ, z (ISO 31-11). David -- David Jonsson Sweden phone callto:+46703000370 -- No virus found in this incoming message. Checked by AVG. Version: 7.5.524 / Virus Database: 269.23.8/1413 - Release Date: 5/3/2008 11:22 AM
